The present invention relates to a method and a device for state estimation in a system for automatic longitudinal and/or transverse regulation in a motor vehicle. Such systems are used, for example, as part of an automatic cruise control in a vehicle for detection of vehicles driving ahead. In these systems (e.g., adaptive cruise control), the traditional cruise control is supplemented by a distance sensor, so it is possible to automatically adjust the speed and/or distance to the traffic situation ahead of the vehicle. To guarantee reliable use in such a system, the function of the system is usually monitored.
German Patent Application 196 44 164 A1 describes a motor vehicle radar system in which a dielectric body is positioned in the path of the beam of the electromagnetic waves for protection against weather effects and preferably also for focusing. To detect and possibly eliminate dirt and coatings of ice, snow or moisture deposited on this dielectric body, the dielectric body has an arrangement of electric conductors. With these conductors, the dielectric body may be heated, the attenuation caused by a possible coating may be measured and a target simulation may be performed for function testing of the radar system. To measure a coating of ice, snow or moisture with this automotive radar system, the dielectric body is covered by two chamber-like arrangements that are tightly interleaved with one another without coming in contact. Each of the chamber-like arrangements is a separate, electrically connected structure. A resistance R and a capacitance C may be measured between these two interleaved arrangements. These values depend on the loss angle tan xcex4 of the material between the two arrangements and thus also on loss angle tan xcex4 of any coating that may be present. In this way, it is possible to determine the signal attenuation caused by a coating and thus the degree of soiling. To perform this measurement of the coating, the electrically conducting arrangement must be applied to the outside of the dielectric body.
An object of the present invention is to provide a method and a device for state estimation in a system for automatic longitudinal and/or transverse regulation in a motor vehicle, so that soiling and/or blindness of a sensor will be determined reliably, rapidly, inexpensively and preferably without additional hardware components.
According to the present invention, this object is achieved by the fact that in a method for state estimation in a system for automatic longitudinal and/or transverse regulation in a motor vehicle, operating according to the radar principle and/or the lidar principle, in particular for detecting soiling and/or blindness of a sensor, the state estimation relies on at least two indicators (In) formed from the signals received and/or transmitted by the sensor.
This implementation offers the advantage that it does not require any additional hardware components, in particular no additional electric conductors on the outside of the sensor, for detection of soiling and/or blindness of a sensor. This is an inexpensive implementation of the method according to the present invention. Instead, the object is achieved via at least two indicators (In) formed directly from the signals received and/or transmitted by the sensor. Thus, rapid and reliable detection of soiling and/or blindness of a sensor is possible directly when the system having the sensor is put in operation and a few measurements have been performed, yielding analyzable results.
The at least two indicators (In) are preferably weighted with weighting factors (an). This offers the advantage that the indicators are weighted according to their different importance for the state of the system.
It is particularly advantageous to link the weighted indicators together. This offers the advantage of forming a linked indicator which has a greater relevance with regard to the stated object than an individual indicator (In).
For the transparency and comparability of the resulting data, it is advantageous for the sum of the weighting factors (an) to be no greater than 1.
It is particularly advantageous that the weighting factors (an) depend on at least one driving situation (Fn) and/or one probability (Vn) which is to be determined. This offers the advantage that the method according to the present invention may be adapted flexibly to various driving situations (Fn) and/or to probabilities (Vn) that are to be determined. It is advantageous here to take into account at least one of the following driving situations (Fn) in determination of the state (P) of the system:
1. The system detects another motor vehicle which is used as the target object for regulation.
2. The system does not detect any possible target object, but the system does detect other moving objects.
3. The system does not detect either a possible target object or any other moving objects.
By taking into account at least one of the aforementioned driving situations (Fn), it is possible to classify the driving situations (Fn) as they are typically differentiated by a system of the generic type.
As probabilities (Vn) to be determined, at least one of the following probabilities (Vn) is selected in the method according to the present invention:
1. The performance of the system is optimal.
2. The performance of the system is not optimal.
3. No functioning of the system is possible.
By determining at least one of the aforementioned probabilities (Vn), a probability (Vn) which unambiguously describes the state (P) of the system is advantageously determined.
Consequently, it is especially advantageous that the linked indicators yield at least one probability (Vn) which makes a statement regarding the probable state (P) of the system. The method is advantageously set up in such a way that the greatest of the probabilities (Vn) describes the state (P) of the system. This yields a state (P) of the system which supplies information regarding the probable state (P) of the system in a single quantity.
It is also advantageous that, as part of the method according to the present invention, the indicators (In) are normalized so that the possible value varies in a range between 0 and 1. This offers the advantage that all the indicators (In) are within one and the same value range, thus facilitating a comparison or an evaluation of the individual indicators (In). In particular in conjunction with the aforementioned interpretation of the weighting factors (an) such that the sum of the weighting factors (an) is no greater than 1, this offers the possibility that the resulting probabilities will also vary in a possible value range between 0 and 1 and will thus directly indicate a probability (Vn) of the system.
It is particularly advantageous that at least one of the following indicators (In) is used in the method according to the present invention:
1. The average angle quality of all objects detected by the system, which permits a statement regarding the quality of the object angle determined.
2. The object stability, which describes the rate of detection failures of the target or control object selected for the vehicle""s longitudinal regulation.
3. The average power of the signals received by the sensor.
4. The sum of all objects detected by the system during a measurement.
5. The linkage of the distance and amplitude of the object detected at the greatest distance.
6. The road surface reflection detected by the system.
The indicators (In) listed above offer the advantage that they have different degrees of prominence depending on different driving situations (Fn). In this way it is possible to make a statement regarding the probable state (P) of the system in almost any driving situation (Fn).
In addition, in the method according to the present invention, it has proven advantageous that a state (P) is assumed to be determined only when the result of the linked indicators is obtained for a predetermined period of time (T). This offers the advantage that short-term changes in probabilities (Vn) due to external influences, for example, do not have a direct effect on the state (P), which is assumed to be determined.
It is advantageous that there are transition states between the probabilities (Vn) and these transition states are also used for analysis. For the case when there is a transition state between two probabilities (Vn), the resulting data may also be used for analysis.
It is a particular advantage of the method according to the present invention that the state (P) of the system thus determined is sent to a control unit which in turns controls a cleaning device for the sensor. This cleaning device is preferably at least a device that works with water, a mechanical cleaning device or a heater for the sensor. This influence on the control of a cleaning device for the sensor offers the advantage that cleaning of the sensor is optimized. In this way, the cleaning device for the sensor may be controlled, for example, in cases in which the control unit would not otherwise have triggered the cleaning device for the sensor.